The present invention relates to liquid dispensers and relates, in particular, to so-called roll-on dispensers wherein a liquid container is formed with an opening defining a socket for receiving a roller in the form of a sphere or a cylinder.
The roller is rotatable in the socket, and by virtue of gravity, adsoption and/or surface tension, liquid material within the container is dispersed at the junction of the roller and the socket.
That is, the roller "picks up" liquid from the interior of the container and as the roller rotates in the socket, the liquid is dispensed through a generally continuous passage defined by the junction of the roller and the peripheral lip of the socket.
Obviously, there must be controlled clearance between the socket and the roller so that the roller can rotate freely and to provide passage for dispensing liquid.
The roller is usually snapped into position within the socket and retained by a socket lip whose peripheral dimension is slightly less than the corresponding dimension of the roller. The liquid container includes a cover or an overcap for protecting the roller and for closing the container.
Some prior art units use stub shafts at opposed ends of a cylindrical roller to support the roller rotatably.
A typical prior art roll-on dispenser utilizing a cylindrical roll is disclosed and described in U.S. Pat. No. 4,840,511 to Fattori et al., issued Jun. 20, 1989.
A spherical roller is incorporated in a liquid dispenser distributed by the CARTER PRODUCTS division of CARTER-WALLACE INC., NEW YORK, N.Y. 10153, packaging ARRID.RTM. EXTRADRY.RTM. antiperspirant and deodorant.
While these roll-on applicators are operable to dispense liquids, there is considerable difficulty in sealing the liquid dispensing passage between the roller and the lip or periphery of the socket into which the roller is seated.
That is, during transit of product from point of manufacture to point of sale, at retail, liquid tends to leak from the container at the space between the socket lip and the roller. Some liquids require agitation (shaking) before dispensing, which also leads to leakage.
This occurrence is obviously undesirable in that leakage mars the package in which the container is displayed and may even leave residue on the display shelf. Frequently, leakage results in liquid collecting inside the cover which spills upon the user when the cover is removed prior to dispensing.
Several compressible media, contained in the cover, such as the resilient liner of the said '511 patent, have been devised to solve the leakage problem with varying degrees of success.